Low-dose systemic bupivacaine prevents the development of allodynia after thoracotomy in rats.
BACKGROUND
Chronic pain after thoracotomy has been recently reproduced in a rat model that allows investigation of the effect of drugs that might reduce the incidence of allodynia after thoracotomy. Previous studies suggest that intrathecal or systemic morphine, clonidine, neostigmine, and gabapentin reduce the incidence of allodynia in the rat postthoracotomy pain model. Our purpose was to test whether intercostal and systemic injection of bupivacaine prevented the development of allodynia in an animal model of chronic intercostal neuropathic pain.


METHODS
Male Sprague-Dawley rats were anesthetized and the right 4th and 5th ribs surgically exposed. The pleura were opened and the ribs were retracted for 1 h. Intercostal or systemic bupivacaine 1 mg (0.2 mL at 0.5%) was injected before and after surgery, or before surgery; a control group underwent rib retraction and did not receive any drug. Rats were tested for mechanical allodynia at a predetermined area around the incision site during the 3 wk after surgery.


RESULTS
Allodynia developed in 43% of the animals that did not receive bupivacaine (control group); in contrast, allodynia developed in only 6%, 12%, and 12% of those animals that received intercostal bupivacaine before surgery, after surgery, or systemically before surgery, respectively.


CONCLUSIONS
Previous studies suggest that allodynia after rib retraction can be prevented by opioids, alpha2-adrenergic agonists, neostigmine, and gabapentin. The current results suggest that bupivacaine is effective in preventing mechanical allodynia, whether given by intercostal injection before or after surgery, or systemically before surgery.
Shin
Jin Woo
JW
Department of Anesthesiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis St., Boston, MA 02115, USA.
Pancaro
Carlo
C
Wang
Chi Fei
CF
Gerner
Peter
P
D000818:Animals; D002045:Bupivacaine / Q000494:pharmacology*; D008297:Male; D017288:Pain Threshold / Q000187:drug effects; D010149:Postoperative Pain / Q000517:prevention & control*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013908:Thoracotomy / Q000009:adverse effects*
D002045:Bupivacaine